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Morphological and genetic analyses in four Italian populations of Lebias fasciata were carried out in order to assess the level of differentiation among populations. Fourteen meristic and 23 morphometric characters, relative to the skull, vertebral column, and the rays of the dorsal and anal fins were examined. In addition, variations at seven gene loci were investigated by allozyme electrophoresis. Both morphological and genetic results showed a noteworthy differentiation among the four populations which reflects their high degree of isolation. Allozyme results indicated that genetic variation is consistent with geographical distribution of these populations, while morphological differentiation cannot be interpreted biogeographically. The lack of dispersion phases in the life cycle of L. fasciata and its limited potential for gene flow account for the genetic divergence among populations. The inconsistency between morphological and genetic results for the two Sicilian populations may account for...

The degree of osteological differentiation of the pharyngeal and oral jaws in five populations of Lebias fasciata was studied. Fourteen morphometric and meristic osteological characters were examined. The results allowed us to differentiate the five populations of L. fasciata and particularly that of Manzonara, living in the Salso river and showing a more evident osteological differentiation. It is probable that the observed morphological differentiation among populations of L. fasciata could be a result of their isolation and that the characters examined could represent partially or totally fixed genetic adaptations.